In copending application Ser. No. 169,294, filed Aug. 5, 1971, now U.S. Pat. No. 3,796,612, there is disclosed a semiconductor structure and method in which moats have been formed and below which regions of higher concentration extend. In connection with the formation of such moats, a problem has arisen in which it appears it is difficult to provide sufficiently thick layers of protective material on the outside corners to act as a mask against the impurity which is being introduced into the semiconductor body to form the regions of higher concentration. This can result in the P+ region at the bottom of the moat shorting out to the P type region at the top of the moat. There is, therefore, a need for a new and improved semiconductor structure and method which overcomes this problem.